Sulfuric acid production plants include those of the sulfur combustion type or waste sulfuric acid combustion type which are designed to generate high-pressure superheated steam useful as a power generation heat source or turbine drive source or for other application by using the heat of sulfur dioxide gas of high temperature produced in the plant. The present invention relates to a method for use in sulfuric acid production plants of such type which is adapted to generate a greater amount of steam by utilizing the heat generated in a drying tower and/or an absorption tower for heating the water to be supplied to a boiler.
The conventional sulfuric acid production plant of the sulfur combustion type has a drying tower for drying air for burning the material, i.e., molten sulfur, with circulating concentrated sulfuric acid, and an absorption tower for causing the circulating concentrated sulfuric acid to absorb sulfur trioxide produced by the conversion of sulfur dioxide. The drying and absorption involve generation of heat, which is not suited for recovery, therefore cooled with cooling water for removal and eventually released into the atmosphere since the circulating concentrated sulfuric acid can not be given a higher temperature because of the limitations imposed on the material used for the circulating acid system.
The development of new materials in recent years has made it possible to raise the temperature of the circulating concentrated sulfuric acid to about 200 to about 220.degree. C. This has led to the proposal of techniques for recovering the heat generated in the drying tower and absorption tower in the form of saturated steam of 500 to 600 kPa(G), whereas the steam is low in pressure and therefore of low value for use as steam.